Most homes today have some form of cooling system in order to make the living space therein more comfortable during the hot summer months. There are several types of cooling systems in use, however the most popular type used in the more humid climates is the “split” type refrigeration system more commonly known as a central air conditioning system. The central air conditioning system generally comprises a condenser coil which cools refrigerant contained therein using ambient air outside the home's enclosure and an evaporator coil and blower assembly which cools the air within the enclosure. The evaporator coil, blower assembly, and primary pan together comprise a fan coil unit which is modular in design for ease of installation and maintenance. Nevertheless, as air is forced passed the evaporator coil by the blower assembly, some of the humidity contained in the warmer air is precipitated as water. Typically, this water is received by a primary pan disposed beneath the evaporator coil and dispensed to the outside environment via a drain line attached thereto.
Although this method of removing condensate from a central air conditioning system does function properly, periodic maintenance is necessary due to several inherent problems encountered with handling the residual condensate or water. First, all metallic parts which are directly exposed to the condensate are susceptible to oxidation or rusting. Drain pans or even drain line connecting means made of metallic materials could potentially develop leaks after long periods of use. Secondly, microbial growths in conjunction with airborne particulates such as dust could become saturated in the condensate pool which causes the drain line to clog thus rendering the entire condensate removal system ineffective.
Current residential building practices have relegated the location of the fan coil unit to the attic of a home. This is due in large part to the relatively large space requirements of the fan coil unit in addition to the close proximity to air ducts thereof, which are generally routed through attic spaces. Because of the aforementioned known problems inherent with existing condensate removal systems, current ‘Building Code’ regulations require some form of redundancy in order to alleviate the possibility of condensate spilling or leaking past the primary drain pan and into open attic spaces. One accepted method is to provide a secondary drain line which is in fluid communication with the primary drain pan but attached at a slightly higher elevation than the primary drain line. Examples of designs utilizing this method are disclosed in U.S. Pat. No. 5,715,697 to Rust et al., U.S. Pat. No. 5,904,053 to Polk et al., and U.S. Pat. No. 5,987,909 to Martin. Nevertheless, this method does not provide sufficient redundancy for a primary pan which has developed a leak due to oxidation or cracks caused by physical stress thereon.
Another accepted method is to provide a secondary pan which is disposed beneath the primary pan in order to catch overflow condensate therefrom. This method requires that the secondary drain pan must be larger in girth than the primary drain pan in order to insure that all possible condensate leaked from the primary pan would be caught by the secondary pan. An optional use of the secondary pan would be to provide a water level detection device that will shut off the central air conditioning system prior to overflow of the pan. Examples of designs utilizing this method are disclosed in U.S. Pat. No. 4,787,212 to Hessey, U.S. Pat. No. 4,937,559 to Meacham, and U.S. Pat. No. 5,921,094 to Bang. A drawback of this type of design is that expensive circuitry and sensing devices must be incorporated utilizing components which are not prone to corrosion in order to provide long serviceable life. Another optional accepted use is to provide a secondary pan which is in fluid communication with a secondary drain line. Thus, each primary and secondary pan would be independently connected to their respective primary and secondary drain lines. This method offers the most comprehensive redundancy to all components of the condensate removal system and is relatively inexpensive to incorporate into a residential cooling system, however due to several inherent drawbacks of current secondary pan designs, this method of condensate removal protection has not enjoyed widespread use. For instance, all secondary pan designs known to the applicant comprise a generally flat bottom surface. This fact virtually insures that there will be some pooling of residual condensate in the bottom of the pan due to slight elevational irregularities over its entire surface. In addition, secondary pans made of metal would suffer from their susceptibility to rusting. An even more ominous problem is the build-up of microbial growths such as mold or mildew within an attic environment exacerbated by stagnant water in the secondary pan.
What is needed is a secondary pan for a central air conditioning system having none of the aforementioned disadvantages as well as an inexpensive means to provide overflow protection thereto. The secondary pan should be able to provide a long serviceable life and be easy to install and maintain.